Subject: Re: Hardware questions
To: Julian C. Dunn <jdunn@aquezada.com>
From: Don Yuniskis <auryn@gci-net.com>
List: port-sparc
Date: 11/26/2001 03:05:49
>Brad Knowles writes:
>At 3:07 PM -0700 on 11/25/01, Don Yuniskis wrote:
>
>> The Classic has 10BaseT w/AUI. The SS1+ and SS2 have AUI.
>> Rather than looking for two different kinds of cards, I
>> figure *use* the RJ45 on the classic for one I/F. Then,
>> *add* an AUI/10Base2 NIC for the *other* I/F. This makes
>> the best use of the existing ports on the Classic and
>> just requires adding at most a 10base2 xceiver (assuming the
>> NIC doesn't have a BNC already on it!)
>
> Just because you've got multiple sockets doesn't mean you
>actually have multiple interfaces.
Correct. You will note that my description (above) claims
*adding* "an AUI/10Base2 NIC for the *other* I/F". Most
NIChips are designed so that you just add another isolation
transformer and you get a second media connection on the
*same* interface. The NIChip either automatically selects
the active connection (by looking for signal activity)
*or* allows you to "manually" select the connection to
use with an appropriate register write.
>I'm 99.99999999% certain that you
>will have just one built-in interface on these machines, although you
>may be lucky in terms of what sockets are provided for you to plug
Correct. That's why the discussion of "should I use the built-in
RJ45 (10baseT) and add a 10base2 SBUS NIC? vs. use the built-in
AUI with a 10base2 transceiver and add a 10baseT SBUS NIC..."
>into. Consider old 3Com 3C509-combo cards that had 10Base-5 AUI,
>10Base2, and 10BaseT all on the same card, even though it was just
>one interface -- you've probably got a similar situation.
>
> Solution: Use only 10BaseT interfaces, and for those machines
>which don't have built-in 10BaseT interfaces, either use an
>AUI/10BaseT transceiver, or buy a second NIC to use.
The problem isn't which *one* media connection to use -- rather,
how best to get one 10baseT and one 10base2 connection ON TWO
SEPARATE I/F's on the same box.
> Myself, I'm quite fond of Quad FastEthernet (QFE) cards -- four
>10/100Base-T interfaces in a single card. Moreover, it will have a
>decent amount of on-board buffer space available, unlike the standard
>built-in interfaces you will find on most machines (you may not see a
>measurable performance hit with 10BaseT, but you will see a higher
>CPU loading as the main processor gets interrupted a lot more to
>handle data).
If you note in my previous comments, I don't run CAT5 between
machines -- RG58 instead (for reasons explained elsewhere).
So, having 4 RJ45's on 4 I/F's is just 3 *wasted* connections
for me :-/
> For a router or firewall, you really, really want to have all
>interfaces running on add-in NICs, so that you can avoid this problem.
Are you stating that the network interface on the motherboard is
implemented in an inferior manner? I.e. no DMA, etc.?
Thx,
--don